Method and apparatus for simultaneously plating and lapping



Feb. 20, 1962 J. M. BAILEY ETAL 3,022,232

METHOD AND APPARATUS PoR s1 TANEOUSLY PLATING AN APPI Filed May 1958 l PIAN( /34 32A EPP -l- B En .5'. ffvGfLxf/vs gms.: L.. HoPPE By J'OHNA .T520

A7 Q J y TTRNEYS United States Patent() 3,022,232 METHOD AND APPARATUS FOR SIMULTANE- OUSLY PLATING AND LAIPIN G John M. Bailey, East Peoria, Fred S. Engelking and James L. Hopper, Peoria, and John P. Jero, Washington, Ill., assignors to Caterpillar Tractor Co., Peoria,

., a corporation of California Filed May 26, 1958, Ser. No.737,887 5 Claims. (Cl. 204-36) This invention relates generally to a method and apparatus for automatically finishing a surface to extremely accurate dimensions. More particularly this invention relates to a plating process and the method and apparatus for plating a surfaceand automatically machining said surface while the object is in the plating solution. Specifically, this invention relates to apparatusfor the deposition of material on the surface to be plated and simultaneously, o: in combination therewith, for performing a lapping operation on the plated surface while the surface is being plated.

The present invention further relates to a method for developing a precision plated surface by lapping said surface while it is being plated, whereby said surface is produced to true and accurate dimensions by a lap which may be used to produce a plurality of subsequent surfaces of like configuration with virtually no change in the size and finish condition of said subsequently produced surfaces.

It is now the practice to plate articles with certain materials to im rove their aesthetic appeal, as well as to protect the surface against wear and corrosion. Depending on the plating material used there are presently known two methods of plate deposition. The most common of these is the electroplating process which utilizes an electric current passing from an anode member to a cathode member (the part being plated) while the partis submerged in a plating solution. Although the process of the present invention may find application in any known method for plating with various materials, the method herein disclosed and described is typical of the electroplating process for the deposition of a'wear resistant surface of chromium or a like substance.

ln some manufacturing processes worn surfaces of an article have been plated with chromium or other abrasion resistant materials to rebuild the worn areas. These surfaces are subsequently machined to an accurate nish to provide a precision it between the plated part and a mechanical component operationally arranged in close association with said plated surface. This machining usually comprises the operation of grinding the plated area so that a close working fit is produced between said components.

Although surfaces of many congurations may be proof diamond charged laps that increase in diameter in increments of a few millionths of an inch. Each lap is,

therefore, forced into a bore that is slightly smaller than the lap in order to remove the excess material. This operation continues until the largest lap produces a bore surface of desired dimension. The pump bore is then selectively fitted with a pump plunger that has been produced to accurate dimensions by other means.

One obvious disadvantage of this practice is the cost of labor required to select the proper plunger for the bore which will produce a fluid tight t between the matv'ce ing parts and the necessity of maintaining these components mated until they are ready for use.

Another disadvantage of the present method of manufacture is the cost of recharging and resizing the diamond charged laps in addition to the tool and labor costs involved in nishing each bore with a plurality of laps of increasing diameter.

Another difficulty presently encountered is in producing a bore surface in a pump barrel wherein said surface is truly cylindrical and capable of restraining the extremely high uid pressures which are customarily imposed on pumps of the types used in fuel injection systems.

It has heretofore been impossible to perform a machining operation on a plated surface While the part 'is in the solution with conventional metal laps because the solution contains acids which cause corrosion of the surface of such laps. It is, therefore, an important object of this invention to provide a tool for machining a plated surface which is made of a material that is not adected by acid' attack, thereby permitting the machining operation to be conducted while the part is in the plating solution.

The present invention is applicable to and has as another of its objects the provision of a method and apparatus for plating and final machining a surface in the 'manner described which surface may be continuous or interrupted, external or internal, cylindrical, or of other regular shapes, for the purpose of producing mating parts to predictable dimensions. The process herein disclosed is applicable also to any plating process for producing an extremely precise finish by simultaneously plating and machining a surface.

An important object of this invention is to provide a method and apparatus for manufacturing components of the type described to such a degree of accuracy as to a lap member constructed of a non-corrosive material' that is harder than the plate deposit which is used to perform a machining operation of the plated surface while the partis being plated.

Still another object of this invention is the provision of a dielectric lap for au electroplating process which comprises means for conducting an electrical current to cause deposition of the plate and perform a lapping operation of the surface plated while the part is in the plating solution.

Another important object of this invention is the provision of a lap member constructed of a ceramic whereby the body of the lap is composed essentially of aluminum oxide and wherein for application in an electroplating process said lap contains anode means for conducting the plating current.

Still another object of the present invention is to proyvide control means associated with the plating apparatus whereby the temperature of the solution may be regulated or altered to compensate for wear of the surface of the lap so that all such plated surfaces produced by the same lap are virtually dimensionally identical after the parts ,Y have cooled.

FIG. 1 is a diagrammatic view of apparatus representative of= the type required for plating a surface and performing a machining operation thereonv while the partis being plated;

FIG. 2 is an enlarged View in elevation'of a combina- Y bination anode and-lap member taken generally along the lines III--Ill ofvFIG. l;V

FG. '4V is a view in elevation showing a modification of FIG. -5V is an enlarged transverse sectional view ofY another modification of the anode and lap membe rhe apparatus for electroplating disclosed herein should ber-considered as typical of only oneV methodY ofv liquid bath plating. Asseen in FiG. of theV drawings, a part to -be plated is clamped in a fixture 1l supported on Y legs 12 or in any suitable manner in the plating solution n lcontained in ar ytanl: 13.

plates 1,4 and 'i5 of :the fixture by` suitable nuts threaded PartA l0 is disposed between to legs 12 to hold the part ltd securely during the plating process.V "FnecntireV fixture 11v and certain surfaces of part 16 `are preferably masked to prevent them fromv being v plated.

Altboughthe surface to be plated may he of various configurations, as heretofore described, the specific surface-to be plated herein disclosed isV in the form of a cylindrical bore (19 extending through the part 1li. Bore surface19 is-machined oversize and iinishedby reamingv or. grinding, but it is to be understood thatno special precautionsrneed be taken inorder to deiine an accurate nish of the surface 19 prior to it being plated.V Y

In the particular arrangement disclosed in FIG. l, part Iltis retained in fixture 11 in such a manner that the axis ofl the boresurface 19. isV disposed in a substantially vertical plane.

Finishing of bore surface 19 as it is being plated is performed by a dielectric lap member 21 preferably having a ceramic body of aluminum oxide or other similar mate- Y rial harder than the plating material. rThe lap is rotated and/or reciprocated byv drive means not shown to perform a machining operation on the plate deposition,V as

will-subsequently be described. Y

-Wheretthe'plateis.deposited by the electroplating process, as shown, part l()V is made oaV conducting material sothat an electrical current may be conducted thereto from a DC. current source 16 throughV a circuit 17 including a contact plate 1S which is held between part 1Y0 and one of the'plate members 14 or 15. Auocle merribers in the form of electrical couductingstrips 2,2,fsuch as lead, are used for chrome plating.

Vline 31 leading to brushes 32 which contact a collector' ring 245: secured to coupling 28, then throughv collector ring 24 to cause electrical current `to iiow. through anodes 22; i Y v Y VThe lap member 21 illustrated in this specific applicationY ofthe invention is iinishedto a very accuratevdiameter, by any well-known machining process. `Ylt willY be understood' that since the platingk solution is usually heatedwhile the part is being plated, the diameter of the lap will not necessarily coincide with the diameter of the iini the combination anode and lap memberV with parts broken v Y 'awayfto show the structural details thereof; andY Yso ' other with the same lap.

ished; bord-but thelinished bore assumes the proper di; Y

varneter upon cooling.

lnperformingthe. process, lap member 21 is inserted into b'ore 19 "through axially aligned, preferably enlarged v "'.ppenmgs sa and s4 provided in pines 14am 15 felpe@- tively. Lap member `21 is rotated and/or reciprocated as A reviously described by means Vnot shown, and under the iniiuence of the electrical current from Vsource 16, deposits of plate begin to formen the surface 19 of part lll. The build-up of chromium is consistent throughout the surface, substantially duplicating every irregularity existing in surface i9. As the process continues the crests of the irregular surface are contacted by the lap Vmember 21. Tdherelative motion of the lap 21 prevents `are relatively completely filled with plate. With this coudition obtaining, lap 21 cont-acts and machines the entire surface to a very smooth and accurate condition.

It is, therefore, possible inY the specific example disclosed to define a linished bore to atopredictable dimension by the deposition of plate onKV the surface of an oversized bore and sirnultaneouslorV in combination therewith, produce an accurate dimension by lapping orA` ruachining said surface While the" parteV is being plated.Y It is further possible within the scope of the present invention to produce the external' surface ofthema'ting pump plunger by this method to such-accurate dimensionsas to permit interchangeability of parts. The lap member applied in this instance would of necessity be affemale memberrhaving the cutting surfaces and anode members inthe internal face of a member ofV substantially tubular shape. Y

Since the plated surface is vlapped, While the plate is beingV deposited, the cutting rate is very light, resulting in a minimum owear on the lap. Conventional means (not shown)v may also be provided to regulate the temperature of the plating solution thereby compensating for the wear Yof'thelap and resulting in the, manufactureVV of subsequent bores that are sizedV virtually identical to each In many instances the rotation and/or reciprocation of the lap will be sutlicient to insure adequate circulak tion of the plating solution between thelap and the part beingv plated. -ijlweven in 'the Varrangeurent disclosedv in FIG. l means are provided' to Vfurnish a positive -liowv ofy the solution, between saidkparts for most` eicientplating ofy the surface. To thisend a pump 36 driven in any suitable manner circulates theV plating solution from tank 13 through aconduit 37 and, pumps the solution through a conduit 38 so aslto cause. it tov flowl through the bore defined by the surface 1Q. The pump discharge conduit 38- is connected to adapter 35,9 securedV to plate l5 of the fixtureV as by capscrews All.V Adapter 39 is preferably counterbored as at l2` so as to permit the lap( to travel axially therein during its reciprocation and to provide a chamber into which the solutionvis pumped. TheY How (yf-solutionv is upwardv between the lap 121 and the ysurface 19, as illustrated in FIG. l, and it is discharged through the topend'by way of opening 33 in` plate 14';V The upwardV ow of' solution minimizes the possibility of entrained gases and air pockets becoming trapped along the surface 19 and insures au even deposit of plate thereon.

twill/,beunderstood that apparatus may4 be provided to conduct the solutionvtothe plating, area without submerg'ing the part andxture in the solutionas previously` n described. Where appropriate, as in a machine having a plurality of plating stations, a closedV circuit comprising a pump 36, line 38, and a; return line (not shown) may be 'used for circulating the plating solution through each offa plurality otxture's. 11 from a commonsupply tank.

'Althouslithe las Structure described is herein disclosedv discs are retained in stacked assembly by a through bolt 46 and secured together by a nut 47 threaded on the end of bolt 46. The ceramic discs 43 are provided with suitable slots 48 defining passages through which the solution is pumped. Simultaneously the peripheral faces of discs 43 lap the plated surface 19 by suitable movement of the lap member 21 as the plate deposit begins to build up suiiiciently to contact the lap surface.

Ceramic bodies of the type described are inherently fragile and where applicable a different structure may be used in order to produce a ceramic lap of a more sturdy structure. To this end a modification of the lap structure is disclosed in FIG. wherein a lap body 51 made of a rigid material such as metal is provided with iiutes 52 to form the core of the lap. Ceramic material, predominantly aluminum oxide or any substance harder than the plating material, may be bonded to the body of the lap, as at 53, and subsequently machined to an accurate dimension for producing a given size. Furthermore, anode strips 54 made of lead or other suitable materials may likewise be embedded within the fiutes of the lap. This structure produces a stronger lap member for performing the process of the present invention. In a construction of this type it may be desirable to mask or insulate theside walls 52a of the fiutes 52 to prevent the plating current from shorting out where the core 51 is made of electrical conducting materials.

The lap member of FlG. 5 may have a core of an electrical conducting material which is soft enough, or coated with material which is soft enough, to permit the surface to be charged with particles of a dielectric maferial (such as aluminum oxide) whereby the plated surface may be lapped while it is in the plating solution. It will be understood that the particle size and the density of the lap surface produced by this process must be controlled to allow the current to pass and still prevent the current from shorting out to the part being plated.

Where the surface to be plated is of a configuration other than cylindrical; as for instance, a square or elliptical bore, a lap of matching configuration carrying anode members is reciprocated relative to the surface while the plate deposition takes place.

Although the specific arrangement as herein disclosed relates to an electroplating process requiring the transfer of an electrical current through anode members in the lap, other lap structures may be used in other plating processes which do not require an electrical current and, therefore, the anode members as well as the electrical circuit will be unnecessary. 'This type of plating system is commonly referred to as electrodeless plating where the plating material is contained in solution in the plating bath and the plate is deposited by the autocatalytic chemical reduction process. The surface being plated is accurately finished by a ceramic lap while the part is in the plating bath as previously described.

Means (not shown) may also be adapted to the drive controls of this mechanism to determine when the plated surface has been completed. As one example of this type of control, a hydraulic transmission has been used to drive the lap. As vthe plated surface nears completion the torque required to turn the lap results in higher uid pressures which are registered on a torque meter to indicate the load imposed. Experiments have indicated that as the load required to drive the lap rises to a certain level, the process is complete.

The disclosure made herein has been specific to the chromium plating process and for this reason the anode means 22, 44, and 54 have been stipulated as being made of lead. It will be obvious that in plating with other materials, appropriate anode materials, soluble or insoluble, may be substituted for the lead anode material disclosed in this application.

We claim: Y

l. An article of manufacture for use in performing a machining operation on a surface of a part being electroplated while said part is in contact with an electrolyte comprising a body made of rigid non-conducting grinding material and having flutes formed therein defining land surfaces therebetween, electrical conducting anode means contained in said flutes and recessed from said land surfaces whereby a plating action will take place on a Work piece in relative motion to said land surfaces and spaced a slight distance therefrom, and said land surfaces will act to control the depth of plate deposited on said work piece.

2. The article of claim l in which the land surfaces are of ceramic material.

3. The article of claim 1 in which the land surfaces and the major portion of the body are formed of ceramic maferial.

4. The method of producing a surface finish to accurate dimensions which comprises immersing a work piece in an electrolytic bath, moving a lap which'has grooves forming intermediate lands conforming to the contour of the surface desired in closely spaced relation to the work piece, and introducing an electric current to said bath through anodes disposed in said grooves to cause plating of the work piece and simultaneously cutting away the deposited plating material until the desired surface conforms in contour to the surface contour of said lands.

5. The method of claim 4 which includes the further step of varying the temperature of the electrolytic bath to compensate for wear of the lap whereby successive work pieces can be produced to the same dimensions with a smaller lap.

References Cited in the le of this patent UNITED STATES PATENTS 1,271,136 Cook July 2, 1918 1,721,949 Edelman July 23, 1929 1,733,404 Fahrenwald Oct. 29, 1929 1,872,290 Hitner Aug. 16, 1932 1,886,218 Olin et al Nov. l, 1932 1,953,955 Crouch Apr. 10, 1934 2,871,177 Comstock Jan. 27, 1959 2,920,026 Kistler Jan. 5, 1960 FOREIGN PATENTS 712,314 Great Britain July 21, 1954 18,643 Great Britain Aug. 18, 1900 of 1899 

4. THE METHOD OF PRODUCING A SURFACE FINISH TO ACCURATE DIMENSIONS WHICH COMPRISES IMMERSING A WORK PIECE IN AN ELECTROLYTIC BATH, MOVING A LAP WHICH HAS GROOVES FORMING INTERMEDIATE LANDS CONFORMING TO THE CONTOUR OF THE SURFACE DESIRED IN CLOSELY SPACED RELATION TO THE WORK PIECE, AND INTRODUCING AN ELECTRIC CURRENT TO SAID BATH THROUGH ANODES DISPOSED IN SAID GROOVES TO CAUSE PLATING OF THE WORK PIECE AND SIMULTANEOUSLY CUTTING AWAY THE DEPOSITED PLATING MATERIAL UNTIL THE DESIRED SURFACE CONFORMS IN CONTOUR TO THE SURFACE CONTOUR OF SAID LANDS. 